/*******************************************************************************
* CogTool Copyright Notice and Distribution Terms
* CogTool 1.3, Copyright (c) 2005-2013 Carnegie Mellon University
* This software is distributed under the terms of the FSF Lesser
* Gnu Public License (see LGPL.txt).
*
* CogTool is free software; you can redistribute it and/or modify
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* the Free Software Foundation; either version 2.1 of the License, or
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*
* CogTool is distributed in the hope that it will be useful,
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* following notices:
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* Eclipse SWT version 3.448
* Eclipse GEF Draw2D version 3.2.1
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package edu.cmu.cs.hcii.cogtool.util;
import java.util.EventObject;
import java.util.Iterator;
/**
* Support for providing a semantic notification to an observer
* of a specific change to an observed subject instance.
* <p>
* A semantic change is described by a subclass of <code>EventObject</code>.
* Clients of this mechanism can associate any information needed to
* describe the specific change that occurred and communicate it to its
* observers.
* <p>
* Observers may indicate that they are only interested in certain
* semantic changes by specifying the subclass of the
* <code>EventObject</code> representing those changes. Such handlers
* will be notified whenever a semantic change occurs that "inherits" (well,
* "is assignable to") that subclass. If one wants to handle all change
* notifications, it is sufficient to use <code>EventObject.class</code>.
* <p>
* Notifications are made in the same order as they were registered.
*
* @author mlh
* @see java.util.EventObject
*/
public interface IAlerter
{
/**
* Add a handler to observe semantic changes raised by this instance
* of the specified semantic type (a subclass of <code>EventObject</code>).
* <p>
* The same handler may be added more than once; if so, it will be
* notified more than once.
* <p>
* Handlers will be invoked in the same order as they were registered.
*
* @param observer the object interested in the semantic event
* @param eventClass the class of the semantic change of interest
* @param handler the handler to be notified of the change
* @param noDuplicates whether to prevent duplicate entries
* @author mlh
*/
public void addHandler(Object observer,
Class<? extends EventObject> eventClass,
AlertHandler handler,
boolean noDuplicates);
/**
* Add a handler to observe semantic changes raised by this instance
* of the specified semantic type (a subclass of <code>EventObject</code>).
* <p>
* The same handler may be added more than once; if so, it will be
* notified more than once.
* <p>
* Handlers will be invoked in the same order as they were registered.
* <p>
* Equivalent to invoking 4-parameter addHandler with noDuplicates = true.
*
* @param observer the object interested in the semantic event
* @param eventClass the class of the semantic change of interest
* @param handler the handler to be notified of the change
* @author mlh
*/
public void addHandler(Object observer,
Class<? extends EventObject> eventClass,
AlertHandler handler);
/**
* Remove the first registration of the given handler as specified
* to observe semantic changes raised by this instance
* of the specified semantic type (a subclass of <code>EventObject</code>).
* <p>
* To remove all registrations, repeat the call to
* <code>removeHandler</code> until it returns <code>false</code>.
*
* @param eventClass the class of the semantic change of interest
* @param handler the handler to be notified of the change
* @return true iff the remove was successful
* @author mlh
*/
public boolean removeHandler(Class<? extends EventObject> eventClass,
AlertHandler handler);
/**
* Remove all registered handlers for observing semantic changes
* associated with the given observer.
*
* @param observer the object interested in the semantic event
* @author mlh
*/
public void removeAllHandlers(Object observer);
/**
* Enumerate all the handler-type pairs registered on this instance.
* <p>
* The returned iterator instance will enumerate
* <code>AlertHandlerEntry</code> instances.
*
* @return an iterator that enumerates all handlers registered
* on this instance
* @author mlh
*/
public Iterator<Alerter.AlertHandlerEntry> getHandlers();
/**
* Enumerate all the handler-type pairs registered on this instance
* that would be invoked if a semantic change of the given type occurred.
* <p>
* The returned iterator instance will enumerate
* <code>AlertHandlerEntry</code> instances.
* <p>
* Note that the given <code>eventClass</code> parameter will "inherit"
* (or "be assignable to") the <code>eventClass</code> value of each
* <code>AlertHandlerEntry</code> instance enumerated.
*
* @param eventClass the class of the semantic change of interest
* @return an iterator that enumerates handlers registered
* to be notified of semantic changes of the
* given "type"
* @author mlh
*/
public Iterator<Alerter.AlertHandlerEntry> getHandlers(Class<? extends EventObject> eventClass);
/**
* Notify all handlers that are interested in the given semantic change.
* <p>
* Only those handlers associated with <code>EventObject</code> subclasses
* that the given <code>alert</code> "inherits" (or "could be assigned to")
* will be notified.
* <p>
* Each handler is notified by invoking its <code>handleAlert</code>
* method with the given semantic change data.
*
* @param alert the data reflecting the semantic change
* @author mlh
*/
public void raiseAlert(EventObject alert);
}